rename 'fontforgeexe/exelibstamp.pre' and 'fontforge/libstamp.pre'
Simplify making FontForge by using libstamp.c and exelibstamp.c instead

One less step. Previous code converted 'pre' to 'c' versions using sed.
Simplify. Not needed anymore
Merge pull request #1066 from JoesCat/master

Convert libstamp.pre and exelibstamp.pre to static files